Field of the Invention
The invention relates to a two-speed automatic planetary transmission.
Description of the Related Art
Existing transmission used for electric vehicles include single-speed reducer, two-speed manual transmission (MT), two-speed automatic transmission (AT), and two-speed automatic mechanical transmission (AMT). All of these have shortcomings.
For example, the single-speed reducer has a fixed speed ratio, as a result, the maximum gradeability, the highest speed, and the optimal work efficiency of an electric motor cannot be achieved synchronously. Therefore, it is proposed to use two-speed transmission. However, the two-speed manual transmission needs manual operation, while the two-speed automatic transmission involves at least an oil pump and a clutch, which increases the size and weight of the transmission, as well as the production cost; besides, the power interruption is prone to appear during the shifting.